language ESSENCE' 1.0

given n : int(1..)
letting ROW be domain int(1..n)
letting COL be domain int(1..n)
find q: matrix indexed by [ COL ] of ROW 

such that  
	allDiff(q),
	allDiff([q[i]+i | i : COL]),
	allDiff([q[i]-i | i : COL])